MLT GlobeKleihauer-Betke test
Blood Bank · also called KB test, Fetal cell count, Acid elution test, Fetomaternal hemorrhage test
What it measures
Counts fetal red cells in the mother's blood using acid elution, which removes adult hemoglobin but leaves fetal hemoglobin. It estimates the size of a fetomaternal bleed to calculate the dose of anti-D immunoglobulin.
Specimen and preparation
- Specimen: Maternal whole blood (EDTA)
- Tube: Lavender top
- Preparation: Collect after delivery or a sensitizing event and before anti-D is given if possible.
Reference range
| Group | Range |
|---|---|
| Adult non-pregnant | <0.01 % fetal cells |
| Fetomaternal hemorrhage (most deliveries) | <2 mL fetal blood |
Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.
Causes of high values
- Fetomaternal hemorrhage (trauma, abruption, delivery)
- Unexplained stillbirth or fetal anemia
- Maternal HPFH or sickle cell disease (false positive)
Method
Acid elution staining of a blood film with microscopic counting; flow cytometry for HbF as an alternative
Good to know
Fetal bleed (mL) ≈ % fetal cells × 50. One 300 µg anti-D dose covers about 30 mL of fetal whole blood.
Related tests
📱 Practise with a timer, track your score and earn certificates in the free MLT Globe app – Google Play or practise online.